CVE-2007-1886 (Integer overflow in the str_replace function in PHP 4.4.5 and PHP 5.2.1 allows context-dependent attackers to have an unknown impact via a single character search string in conjunction with a single character replacement string, which causes an "off by one overflow.")
CVE-2007-1885 (Integer overflow in the str_replace function in PHP 4 before 4.4.5 and PHP 5 before 5.2.1 allows context-dependent attackers to execute arbitrary code via a single character search string in conjunction with a long replacement string, which overflows a 32 bit length counter. NOTE: this is probably the same issue as CVE-2007-0906.6.)